I was googleing spots last night and came across this.
Used to surf in that area way back in 97 but I always thought that the river that ran into the corner was an overflow from the vlei which was safe. I remember a sign being put up but the warning was for an overgrowth of algae which might affect you mildly if you ingested it not phosporous and e-coli from a sewerage farm hidden behind the factories.
Found this article
http://www.kommetjie.org/newsold.php?mode=view&IQ=52 (under the heading wildevoelvlei)
Anyone know anything more about this?